1. Field of the Invention
The present general inventive concept relates to a multi-channel speaker system, and more particularly, to a method and an apparatus to reproduce a multi-channel audio signal that performs mixing of a signal of a center channel to left and right channels in a home theater system.
2. Description of the Related Art
Recently, home theater systems have been developed and launched. Home theater systems reproduce video and audio that are recorded in various recording media such as DVDs, HDDs, tapes or the like and output the video reproduced from the recording media onto wide screen televisions.
In addition, home theater systems separate and output audio channels of audio reproduced from recording media, for example, multi-channel audio of 5.1 channel surround sound that is reproduced from DVD through six speakers that are separated and equipped at different locations.
In addition, home theater systems simply perform mixing of audio signals of left and right channels and output the audio signals of the left and right channels as an audio signal of a center channel.
However, in home theater systems, speech cannot sometimes be clearly conveyed to a listener due to the volume of the center channel, locations of speakers, a difference in speaker units or the like.
FIG. 1 is a conceptual view illustrating an effect of a time-delayed signal, which occurs according to a listener's location in conventional mixing of a center sound.
When two sounds having the same frequency and sound pressure are simultaneously reproduced through two speakers in a conventional stereo system, the two sounds sound like a sound generated from the front center with respect to human ears. Likewise, when a sound image is positioned in the front center of speakers, it is said that ‘a sound image is localized. The localization of the sound image is determined according to level, phase and time differences between each of the left and right speakers and a listener. When the same sounds are heard in different directions after a certain interval, a last sound is masked by a first sound. Accordingly, the listener can hear in a direction of a sound source of the first sound. This phenomenon is known as a “precedence effect,” “Haas effect” or “first front wave law.”
Referring to FIG. 1, two speakers SL and SR are arranged at left and right sides, and a listener is positioned in the front center of the two speakers. A sound signal is directly input to the left speaker SL, and a sound delayed by a time τd is input to the right speaker SR. When the delayed time difference (τd)=0 ms, that is, when left and right signals simultaneously arrive at the ears of the listener, the sound image is positioned in the center A of the two speakers SL and SR. As the delayed time difference τd gradually increases, the left signal arrives more quickly at the ears of the listener than the right signal, and the sound image is gradually moved towards a left side. A moving degree of the sound image is gradually changed according to the type of sound source and the listener's location. However, the sound image is moved in proportion to the time difference τd towards each speaker from the center of the speakers at a time difference of less than 1 ms. The sound image sounds as if a sound is output from only one speaker at a time difference in the range of 1 to 30 ms.
Accordingly, when a listener is closer to one speaker than other speakers, a center sound, on which mixing is performed, may be heard from only one speaker, which is closest to a listener, using a conventional mixing manner of a center sound.